First, the classification of vegetable temperature requirements
According to the different requirements of various vegetable temperature conditions and tolerable temperatures, vegetable plants can be divided into five categories.
1. Cold-tolerant perennial perennial vegetables: including leeks, daylilies, and Ishigaki. During the growing season, the above-ground parts are resistant to high temperatures, and they die in the winter season. They survive winters in underground roots (stems) and are able to withstand low temperatures of -10°C.
2, cold-resistant vegetables: including spinach, Chinese wolfberry, green onions, onions, garlic, etc., the best growth at 15 ~ 20 °C, energy -1 ~ -2 °C low temperature.
3, semi-hardy vegetables: including cabbage, cabbage, radish, carrots, cabbage, peas, beans, etc., grow best at 17 ~ 20 °C, able to withstand the short-term temperature of -1 ~ -3 °C.
4, thermophilic vegetables: including cucumbers, tomatoes, peppers, beans, eggplant, etc., growth temperature of 20 ~ 30 °C, intolerance to frost, 15 °C easy to cause falling, above 35 °C growth and poor fruiting.
5, heat-resistant vegetables: including melon, pumpkin, watermelon, cowpea, concanavalin, leek, spinach, etc., about 30 °C growth is good, 35 ~ 40 °C can still grow normally, strong.
Thermophilic and heat-tolerant vegetables are intended to be cultivated in winter. They must be cultivated in protected areas such as greenhouses. Cold-tolerant or semi-cold-resistant vegetables are required to be cultivated in summer and early autumn. Shade-covering measures or anti-season alpine cultivation should be adopted.
Second, the temperature cycle and vegetable production
The response of vegetable crops to the cyclical changes in day and night temperatures is called the vegetable temperature cycle. The higher temperature required for vegetable crops during the day is beneficial to photosynthesis, while the lower night temperature can reduce the consumption of stored materials and facilitate the transportation and storage of assimilation products.
There is a certain range of temperature difference between day and night, night temperature can not be too low, because the vegetable crops still grow at night, constantly absorbing water and nutrients. Therefore, we must pay attention to the protection of the day and night temperature management, in the eyes full of light, the temperature difference between day and night should be larger, and the temperature difference between day and night should be smaller.
The temperature cycle has important significance for guiding the cultivation of vegetables. For example, when the seeding season is determined, the formation time of the product organs is arranged in a time period of large temperature difference between day and night, so as to facilitate the accumulation of nutrients and promote the enlargement of the product organs. Another example is the use of daily and warm nights management at different times during nursery to promote and control the growth of seedlings and cultivate strong seedlings. When cultivated on protected land, the temperature and night temperature of the earthworms are often controlled in several stages according to the weather. For example, the sunny day's temperature is 2~5°C higher than the cloudy day, and the sunny night temperature is 1~4 higher than the cloudy day's. °C, the temperature in the afternoon is 2~5°C lower than the afternoon temperature, and the temperature is higher in 3~4 hours after sunset, so as to facilitate the nutrient operation, and then the temperature continues to decrease, so that the nutrient consumption is kept to a minimum.
Third, the influence of soil temperature on the growth of vegetables
In a certain range, the soil temperature increases and the growth speeds up. The optimum temperature for the absorption of various types of vegetable roots is different. The higher the soil temperature is for the growth of thermophilic vegetable roots. The suitable temperature for root elongation and penetrating the soil is 18~20°C. The roots of cucumber and sweet pepper are very sensitive to low temperature. .
In the winter and spring of vegetable production, watering should be controlled to prevent lowering of ground temperature and affect root growth and absorption. Raise the ground temperature and protect the soil by measures such as cultivating loose soil or covering the film. In winter and spring, soilless cultivation of thermophilic vegetables often results in poor growth due to low water temperature. Therefore, raising the temperature of the nutrient solution cannot be ignored. Too high soil temperature also affects growth. When the soil temperature exceeds 25°C, the root absorption capacity also weakens. When the soil temperature exceeds 30°C to 35°C, the growth of the root system is inhibited and it is susceptible to disease, causing premature plant failure. In summer, small water is used for pouring, earth-covering and surface-covering methods to reduce ground temperature and protect the root system. In addition, water should not be suddenly watered at noon during the vigorous summer season, causing a sudden drop in rhizosphere temperature and causing the plants to wilt or even die.
Fourth, the high temperature, low temperature damage to the growth of vegetables
(a) high temperature hazards
1. High temperatures are accompanied by strong light, causing plants to lose water and wilting, affecting growth. If water does not keep up, it may cause plant death.
2, high temperature affect pollen vigor, resulting in eggplant, bean vegetables fall, reduce the rate of fruit set, abnormal fruit increased.
3, high temperature and light easily make tomato, watermelon, melon, pepper fruit burning.
4, high temperature and strong light caused by weakened photosynthesis, increased respiration, resulting in a lack of internal nutrients, poor growth.
5, affect the flower bud differentiation and sex differentiation: high temperature and long sunshine often make the male male flower increased, female flower differentiation late. When tomato and pepper flower buds are differentiated, they spend less and are stunted under high temperature conditions.
6, affect the formation of normal pigmentation, tomato at high temperatures (more than 35 °C), lycopene is difficult to form normally, so the fruit often appears yellow, red and white colors and white noise, greatly reducing the value of the goods.
High-temperature cultivation of the first choice of heat-resistant varieties, in addition to high temperature during the morning and evening can be used to cool the water, puddle cooling, shade net coverage or cooling effect from the ground cover, winter and spring small shed, greenhouse cultivation on sunny days should pay attention to ventilation and cooling to avoid High temperature damage.
(b) Low temperature hazard
Cold hazards can be divided into cold damage and cold damage. Cold injury, also known as cold injury, refers to the damage of vegetables at temperatures above 0°C; freezing injury refers to the phenomenon of vegetables suffering from freezing at temperatures below 0°C and freezing in the body.
1, solanaceous vegetables, melons, beans and vegetables encountered low temperatures, often caused by falling flowers, affecting pollen vitality, and even no powder, affecting fruit rate, resulting in malformed fruit.
2. Low temperature often causes biennial vegetables (such as cabbages, cabbages, and root vegetables) to be convulsed when the product organs are not formed or formed in the process, that is, convulsions in advance.
3. Freezing damage below 0°C often causes tissue damage, dehydration and dryness, leading to plant death.
4, low temperature hindered the normal growth of vegetables, affecting root water absorption, leading to imbalance in water supply, the plants may be wilting, inhibiting the formation of chlorophyll, resulting in leaves yellow or yellow-white, this is the typical symptoms of cold vegetables, cold damage.
5, hi temperature vegetables in early spring sowing, often resulting in bad species, seedlings encounter low temperature and rainy days, the leaves gradually turn yellow, brown root rust, lateral roots, root hairs died, wilting above the ground, commonly known as "roots down seedlings."
Cultivation can be used on cold-resistant varieties, seedlings for low-temperature hardening seedlings, increased phosphorus and potassium fertilizers, to prevent leggy, improve the quality of seedlings or plants can enhance the cold resistance, can also be used irrigation or foliar spray, improve The approach to air humidity near the ground mitigates freezing damage. The most effective way can be to use plastic film covering cultivation measures or smoke, geothermal heating and other measures to prevent cold damage.
V. Vernalization and Vegetable Production
Two-year-old vegetables (such as Chinese cabbage, cabbage, celery, spinach, radish, etc.) require certain low-temperature conditions before convulsing and flowering. This physiological process that requires a period of low-temperature period to twitch and blossom is called the "spring-based phenomenon." Or the vernalization stage. Through the vernalization stage, flowering takes place during long days and at higher temperatures. The conditions required for the two-year-old vegetables to pass through the vernalization stage vary according to the type of vegetables and can basically be divided into two categories.
1. Seed vernalization vegetables: such as cabbage, radish, mustard and spinach, lettuce, etc., they can pass the vernalization stage at any suitable period of time since the seed germination, and then pass long-day sunshine. At higher temperatures, it twitches and blossoms. The temperature required for vernalization of most vegetables is 0~10°C, preferably 2~5°C. The vernalization temperature of some vegetable varieties or varieties can be stable to about 15°C or higher. The continuous low temperature time required is 10~30 days. . The temperature range required for this type of vegetable through the vernalization stage is relatively wide, the time required is short, and it is easy to encounter such conditions in production. Therefore, the variety is improperly selected, the planting period is not properly arranged, and it is relatively easy to form the product before or during organ formation. In the case of convulsions and flowering, this phenomenon is called "pre-convulsive" or "unripe convulsions." For example, spring Chinese cabbage should use varieties of “Yangchun†and “spring generalsâ€. The required temperature during the vernalization stage of this variety is low, and the duration is longer, so it is not easy to borrow money in advance. Cabbage is a seed vernalization type, should be used to raise the ground wire to avoid seedlings affected by low temperature, causing convulsions, in addition to the sowing date can not be too early and the use of plastic film cover cultivation. For the anti-season cultivation of Chinese cabbage, the choice of sowing date is very important. For example, the “Xiayang†cabbage in the high mountains (800 meters above sea level) was sown in early April, which could lead to non-balling and convulsions.
2, green body (seedlings) Vernalized vegetables: such as cabbage, onions, celery, etc., they must be in the seedlings grow to a certain size, in order to feel the effect of low temperature through the vernalization stage, the germination of the seeds of these vegetables and low temperature Too young seedlings basically do not work.
Plants of a certain size are usually expressed by indices such as leaf number and stem diameter.
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